Explosion and Fire: Chevron Pembroke Refinery, 2 June 2011

Reminder of the Risks and Precautions Associated with Tank Cleaning Operations

by Ron De Cort. Head of Operations, Wales and West of England, Hazardous Installations Directorate, HSE

Following the incident at the Chevron Pembroke Refinery on 2nd June HSE, on behalf of the COMAH Competent Authority, would like to remind site operators of the dangers associated with this type of operation and of the guidance available to ensure the work is undertaken safety.

Tank cleaning operations were in progress within the amine recovery unit at the refinery site when there was an explosion and subsequent fire. The incident led to the death of four people and serious injuries were sustained by another person. The joint police and COMAH Competent Authority investigation team is working to establish the cause of the incident.

The risks associated with tank cleaning are widely recognised in the major hazard industries and there are well established control measures. These are outlined in:

Site operators should review their arrangements for cleaning tanks that contain hazardous substances and ensure that they meet current good practice.

Full investigation report

Investigation findings and safety management lessons for industry.


The refinery is a top tier establishment under the Control of Major Accident Hazards Regulations 1999 (as amended). The Environment Agency (EA) in England and Wales, Scottish Environment Protection Agency (SEPA) in Scotland, and the Health and Safety Executive (HSE) are jointly responsible (as the Competent Authority) for regulating major hazardous industrial sites in the UK under the Control of Major Accident Hazard Regulations 1999 (COMAH).

COMAH requires operators of major hazard sites subject to the Regulations to take all measures necessary to prevent major accidents and limit their consequences to persons and the environment. Operators of top tier COMAH sites are also required to submit written safety reports to the Competent Authority; and to prepare emergency plans to deal with the consequences of a major accident. Operators and others (including contractors, designers and suppliers) also have relevant duties under the Health and Safety at Work etc Act 1974 and under other environmental legislation to protect land, air and water, including the Water Resources Act 1991.

The incident occurred on Thursday 2 June and is under investigation by Dyfed-Powys Police and HSE. The Police currently have primacy in accordance with the Work Related Deaths Protocol.

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